I do not quite understand what is so funny in this? After all, he could have been working with tissue lysates, serum/plasma or tissue culture supernatants and study the proteins in there...

Anyway, sounds bit odd that your antibodies would bind such a big range of molecules. Although if your target protein has some variable region or odd glycosylation patterns and your antibody only targets the "constant" region, extra bands might appear. But if the cell line is truly homologous, I doubt what you see is really all the protein isoforms.

Is the protein intracellular, membrane-bound or secreted? Some extra information on this protein might help, with this we cannot say much.

I understand that may question may well be funny, but I am affraid my supervisor is not going to laugh as much when I show him my blots.

JackBean, I found the isoforms for the protein on http://www.ensembl.org/index.html. For 16 of them it is written " Protein coding", for the rest - "No protein product". However, on NCBI you can find only 8 of them.

I used two antibodies from two different companies, but the result is the same.

Biohazard, the cell lysate I have used is from hypotetraploid cells with average chromosome number 84. the protein is a transcription factor with MW, with respect to the different isoforms, ranging from 2-55kDa. However, most of the isoforms are about 50-55kDa and yes they have glycosylation sites, so they would appear at ~60kDa.